Recently, when excavating a well such as an oil well or a gas well, a system called MWD or LWD for acquiring well information and stratum information while performing excavation has been used in order to improve efficiency of well trajectory management, reduce costs and enhance safety, etc. For example, in the MWD system, a drill string having at the lower end a bit for excavating the stratum is provided with sensors for detecting a load and a torque of the drill bit, and sensors for detecting a position, a direction and the like of a well, etc., and detected information from the sensors is transmitted to the ground using electromagnetic waves, pressure waves, acoustic pulses or the like (see, for example, Patent Literature 1). Alternatively, the drill string is drawn out from the well during a well excavation process or after completion of excavation, and measurement devices and sampling devices are inserted into the well to perform various kinds of measurements and sampling of stratum fluids (see, for example, Patent Literature 2).